Simplified characteristic time method for accurate estimation of the soil hydraulic parameters from one‐dimensional infiltration experiments

Recently, a novel approach with excellent performance based on the concept of the characteristic infiltration time, the characteristic time method (CTM), is proposed to infer soil sorptivity ( S ) and saturated hydraulic conductivity ( K s ) from one‐dimensional (1D) cumulative infiltration. The current work provides a simplified version of the CTM, called the SCTM, by eliminating the necessity of the iteration method used in CTM and providing a similar accuracy as the original method when estimating S and K s . We used both synthetic and experimental data to evaluate SCTM in comparison with the original CTM, as well as Sharma (SH) and curve‐fitting methods. In the case of synthetically simulated infiltration experiments, the predicted S and K s values showed an excellent agreement with their theoretical values, with Nash–Sutcliffe ( E ) values higher than 0.9 and RMSE values of 0.11 cm h 1/2 and 0.35 cm h –1 , respectively. In the case of experimental data, the SCTM showed E values larger than 0.73 and RMSE values of 0.64 cm h 1/2 and 0.35 cm h –1 , respectively. The accuracy and the robustness of SCTM was comparable with the original CTM when applied on synthetic infiltration curves as well as on experimental data. Similar to the original CTM, the simplified approach also does not require the knowledge of the time validity, which is needed when using approaches based on Philip's infiltration theory. The method is applicable to infiltrations with durations from 15 min to 24 h. The supplemental material presents the calculation of S and K s using SCTM in an Excel spreadsheet.